The present invention relates in general to apparatus for cleaning wires, and in particular to a wire cleaner using electric current to cathodically remove impurities from an elongated wire workpiece, such as welding wire.
Cathodic cleaning is commonly used to clean aluminum or superalloy workpieces prior to and during welding processes. In cathodic cleaning, an electric arc is established between the workpiece surface and an electrode, causing electrons to be emitted from the workpiece surface (i.e., the workpiece is the cathode, hence the name "cathodic" cleaning). The electron emission from the workpiece removes contaminants from the workpiece surface, thereby cleaning it of impurities. However, there are no known devices for continuously cathodically cleaning elongated lengths of welding wire prior to or during a welding process.
Magnetic fields are often used to affect an electric discharge, such as a welding arc, to cause the arc to rotate during a welding process. The welding arc is subjected to a stationary or moving, external magnetic field. One application of this method is the Magnetically Impelled Arc Butt (MIAB) welding process.
A cold sputter type of wire cleaner is disclosed in U.S. Pat. No. 4,935,115, in which a "long metal substrate" is continuously fed through a sputtering chamber vacuum, where a high electric potential between the substrate and an anode causes inert gas ions to bombard the substrate. The sputtering action of the inert gas ions cleans impurities from the wire; it does not form an arc to clean the wire. Because this device requires a vacuum to operate, long segments of wire must be fed through seals in the sputtering chamber to maintain the vacuum.
Other known wire cleaners use mechanical or chemical processes to clean welding wires. These processes are relatively time consuming, cumbersome, or inefficient. Common examples of the former processes include abrasive contact with the wire, while examples of the latter involve submersion of the wire in an acid or solvent bath to remove contaminants from the surface of the wire.
Applicant's earlier invention as set forth in U.S. patent application Ser. No. 08/706,124 filed Aug. 30, 1996 entitled DEVICE FOR CATHODIC CLEANING OF WIRE, will accomplish cathodic wire cleaning at wire feed rates in the range of 15 inches per minute (ipm). However, at the low electrical current levels employed therein, the electric arc established between the wire and the surrounding arc ring can sometimes become unstable.
It is thus clear that an apparatus which could provide faster high speed cleaning of welding and other wires just prior to use, and which would not require a vacuum environment or chemical solutions of acids or other solvents, would be welcomed by the industry.